JP5832457B2 - Medium conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a medium conveying apparatus and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copier, a facsimile machine, a multifunction machine, for example, a printer is provided with an image forming unit, an LED head, a transfer roller, a fixing device, a paper cassette and the like. The image forming unit includes a photosensitive drum, a charging roller, a developing roller, a developing blade, a toner supply roller, a cleaning blade, a toner cartridge, and the like. The toner is stored in the toner cartridge, and is stored in a paper cassette. Paper is stored.

  In the image forming unit, the surface of the photosensitive drum uniformly charged by the charging roller is exposed by the LED head to form an electrostatic latent image. The toner supplied from the toner cartridge to the main body of the image forming unit, that is, the image forming unit main body, is supplied to the developing roller by the toner supply roller, and the toner on the developing roller is thinned by the developing blade. Then, the toner on the developing roller is attached to the electrostatic latent image on the photosensitive drum, and the electrostatic latent image is developed to form a toner image on the photosensitive drum.

  The paper fed out from the paper cassette is separated one by one by a pair of paper feed rollers, and after skewing is corrected, the paper is sent to a transfer portion between the photosensitive drum and the transfer roller, and the toner is transferred by the transfer roller. The image is transferred.

  Then, the sheet on which the toner image is transferred is sent to a fixing device, and the toner image is fixed on the sheet in the fixing device to form an image. The paper on which the image is formed in this manner is discharged out of the printer main body, that is, the apparatus main body.

  In order to correct the skew of the paper fed out from the paper cassette, a roller transport mechanism as a medium transport device is disposed along the paper transport path, and the roller transport mechanism is a registration roller as a first roller. , And a pair of registration rollers including a pressure roller as a second roller disposed to face the registration rollers (see, for example, Patent Document 1).

JP 2004-83203 A

  However, in the conventional roller transport mechanism, a spring as an urging member that presses the pressure roller against the registration roller with a predetermined urging force needs to be disposed on the pressure roller side, so the roller transport mechanism is downsized. I can't. As a result, the printer cannot be downsized.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a medium conveying apparatus and an image forming apparatus that can solve the problems of the conventional printer and can be miniaturized.

  Therefore, in the medium transport device of the present invention, the pressed member, the first holding portion that holds the pressed member, the pressing member disposed to face the pressed member, and the first And a second holding portion that holds the pressing member, and an urging member that presses the pressing member against the pressed member.

  The first holding unit includes a first urging member holding unit that holds one end of the urging member.

  The second holding portion includes a second urging member holding portion that holds the other end of the urging member.

The second urging member holding portion is disposed downstream of the first urging member holding portion in the direction in which the pressing member is pressed against the pressed member.
The urging member is a compression spring, and is disposed between the first urging member holding portion and the second urging member holding portion.

  According to the present invention, in the medium transport device, the pressed member, the first holding unit that holds the pressed member, the pressing member disposed to face the pressed member, and the first And a second holding portion that holds the pressing member, and an urging member that presses the pressing member against the pressed member.

  The first holding unit includes a first urging member holding unit that holds one end of the urging member.

  The second holding portion includes a second urging member holding portion that holds the other end of the urging member.

The second urging member holding portion is disposed downstream of the first urging member holding portion in the direction in which the pressing member is pressed against the pressed member.
The urging member is a compression spring, and is disposed between the first urging member holding portion and the second urging member holding portion.

  In this case, one end of the biasing member is held by the first biasing member holding portion, the other end of the biasing member is held by the second biasing member holding portion, and the biasing member is the first biasing member. Since it is disposed between the holding portion and the second urging member holding portion, the structure of the medium transport device can be simplified. In addition, the urging force of the urging member can be reliably transmitted to the pressing member via the second holding portion, and the pressing force necessary to transport the medium can be sufficiently generated.

  Furthermore, the structure outside the pressing member in the medium conveying device can be simplified. As a result, the medium conveying device can be reduced in size, and the image forming apparatus can be reduced in size.

It is a perspective view which shows the roller conveyance unit in the 1st Embodiment of this invention. 1 is a schematic diagram of a printer according to a first embodiment of the present invention. It is sectional drawing which shows the principal part of the 1st roller conveyance mechanism in the 1st Embodiment of this invention. It is a disassembled perspective view which shows the principal part of the 1st roller conveyance mechanism in the 1st Embodiment of this invention. It is sectional drawing which shows the principal part of the 2nd roller conveyance mechanism in the 1st Embodiment of this invention. It is a disassembled perspective view which shows the principal part of the 2nd roller conveyance mechanism in the 1st Embodiment of this invention. It is a 1st figure for demonstrating operation | movement of the 1st roller conveyance mechanism in the 1st Embodiment of this invention. It is a 2nd figure for demonstrating operation | movement of the 1st roller conveyance mechanism in the 1st Embodiment of this invention. It is a perspective view which shows the roller conveyance unit in the 2nd Embodiment of this invention. It is a figure which shows the principal part of the 2nd roller conveyance mechanism in the 2nd Embodiment of this invention. It is a figure for demonstrating operation | movement of the 2nd roller conveyance mechanism in the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer as an image forming apparatus will be described.

  FIG. 2 is a schematic view of the printer according to the first embodiment of the present invention.

  In the figure, Pr is a printer, and the printer Pr corresponds to the image forming unit 12 provided with a photosensitive drum 14 as an image carrier, and corresponds to the image forming unit 12, and the photosensitive drum 14. A transfer roller 20 as a transfer member disposed corresponding to the image forming unit 12 and facing the photosensitive drum 14, and fixing. A fixing device 33 as an apparatus is provided.

  The image forming unit 12 is detachably disposed with respect to the main body of the image forming unit 12, that is, the image forming unit main body 12a, and the image forming unit main body 12a, and stores a developer as a developer. A toner cartridge 12b as a unit. In addition to the photosensitive drum 14, the image forming unit main body 12a includes a charging roller (not shown) as a charging device, a developing roller as a developer carrying member, a developing blade as a developer regulating member, and a developer. A toner supply roller as a supply member, a cleaning blade as a cleaning member, and the like are disposed.

  In the image forming unit 12, the surface of the photosensitive drum 14 uniformly charged by the charging roller is exposed by the LED head 13 to form an electrostatic latent image as a latent image. The toner supplied from the toner cartridge 12b into the image forming unit main body 12a is supplied to the developing roller by the toner supply roller, and the toner on the developing roller is thinned by the developing blade. The toner on the developing roller is attached to the electrostatic latent image on the photosensitive drum 14, and the electrostatic latent image is developed to form a toner image as a developer image on the photosensitive drum 14. .

  Further, a sheet cassette 34 as a first medium stacking section and as a medium storage section is detachably disposed in the main body of the printer Pr, that is, the lower portion of the apparatus main body. A sheet as a medium is stacked and stored on a medium stacking plate 101 that is swingably disposed in the sheet cassette 34.

  A first medium feeding portion 21 for feeding sheets one by one is disposed on the feeding side of the sheet cassette 34, that is, the front end. The first medium feeding portion 21 is disposed so as to come into pressure contact with the front end of the sheet that has risen to a predetermined height as the medium stacking plate 101 rotates, and is a pickup as a feeding roller for feeding the sheet. A roller 103, a feed roller 105 as a first discriminating roller and as a feed mechanism for separating sheets fed by the pickup roller 103 one by one and supplying them to the medium transport path Rt1, and A retard roller 107 is provided as a second discriminating roller and a retard mechanism. The feed roller 105 and the retard roller 107 constitute a discriminator and a pair of paper feed rollers.

  In addition, a manual sheet feeding unit (not shown) serving as a second medium stacking unit is disposed on the side of the apparatus body so as to be swingable with respect to the apparatus body, and the manual sheet feeding unit stacks sheets. And a second medium feeding unit that has the same structure as the first medium feeding unit 21 and feeds the sheets of the manual tray one by one and supplies them to the medium transport path Rt2.

  A first roller conveyance mechanism 111 as a first medium conveyance device is disposed downstream of the first roller conveyance mechanism 111 on the downstream side of the first medium feeding unit 21 in the medium conveyance path Rt1. A second roller transport mechanism 113 as a second medium transport device is provided, and the first roller transport mechanism 111 is fed by the first medium feed unit 21 and supplied to the medium transport path Rt1. The second roller transport mechanism 113 temporarily feeds the sheet fed by the second medium feeding unit and supplied to the medium transport path Rt2 by correcting the skew by temporarily stopping the sheet. After the skew is corrected by stopping automatically, the sheet is transported and supplied to the medium transport path Rt3.

  Note that while the paper supplied from the paper cassette 34 is being transported, the paper is not supplied from the manual paper feeder to the medium transport path Rt2. In addition, even when the sheet whose skew has been corrected by the first roller transport mechanism 111 reaches the second roller transport mechanism 113, the skew is corrected again by the second roller transport mechanism 113. Without being conveyed and supplied to the medium conveyance path Rt3.

  The first roller transport mechanism 111 serves as a drive roller that is a first roller that is rotated by a rotation from a transport motor as a medium transport drive unit (not shown), and as a pressed member. The registration roller 22 is disposed so as to face the registration roller 22 and to be movable toward and away from the registration roller 22. A pressure roller 23 as a driven roller and as a pressing member, and a spring 143 as a biasing member that presses the pressure roller 23 against the registration roller 22. The registration roller 22 is rotatably fixed at a predetermined position on a frame member 42 (FIG. 1) to be described later, whereas the pressure roller 23 includes a registration roller 22 and a pressure roller. When the sheet passes between the registration roller 22 and the pressure roller 23, it is arranged so as to be able to move slightly on a line connecting the respective axes 23 (normal lines of the registration roller 22 and the pressure roller 23). Further, it moves away from the registration roller 22 corresponding to the thickness of the paper. The registration roller 22 and the pressure roller 23 constitute a first registration roller pair as a skew correction roller pair.

  Further, the second roller transport mechanism 113 is a first roller that is rotated in response to rotation from the transport motor, a registration roller 24 as a driving roller and a pressed member, The second roller is arranged to be opposed to the registration roller 24 and movable in the contact / separation direction with respect to the registration roller 24, and is rotated along with the rotation of the registration roller 24 in a contact state. A pressure roller 25 as a driven roller and as a pressing member, a spring 143 as a biasing member that presses the pressure roller 25 against the registration roller 24, and the like. The registration roller 24 is rotatably fixed at a predetermined position on the frame member, whereas the pressure roller 25 is on a line connecting the axes of the registration roller 24 and the pressure roller 25. When the sheet passes between the registration roller 24 and the pressure roller 25, the sheet moves away from the registration roller 24 corresponding to the thickness of the sheet. The registration roller 24 and the pressure roller 25 constitute a second registration roller pair as a skew correction roller pair.

  The registration rollers 22 and 24 are formed by winding an insulating rubber as an insulating layer around a shaft made of a metal material which is a conductive material, in this embodiment, stainless steel, and the pressure roller. Reference numerals 23 and 25 are formed of a metal material which is a conductive material, and in the present embodiment, a roller made of stainless steel.

  The sheet transported through the medium transport paths Rt1 and Rt2 is supplied to the medium transport path Rt3, and is transported between the photosensitive drum 14 and the transfer roller 20 by the transport roller pair 120 disposed in the medium transport path Rt3. The toner image on the photosensitive drum 14 is transferred to a sheet at the transfer portion p1.

  The fixing device 33 is disposed on the downstream side of the transfer portion p1 in the medium transport path Rt3. The fixing device 33 includes a fixing roller 29 as a first fixing roller having a heating element (not shown) such as a halogen lamp therein, and a second fixing roller disposed to face the fixing roller 29. The toner image on the paper is heated and pressed by the fixing roller 29 and the backup roller 30 to be fixed on the paper to form an image.

  Further, on the downstream side of the fixing device 33 in the medium transport path Rt3, transport roller pairs 123 and 124 and a discharge roller pair 126 are disposed, and the sheet on which the image is formed is the roller pairs 123 and 124. , And is discharged out of the apparatus main body by the roller pair 126 and stacked on the stacker 39.

  The roller pairs 120, 123, 124, and 126 constitute a roller conveyance mechanism as third to sixth medium conveyance devices together with a spring (not shown).

  Next, a roller conveyance unit composed of the first and second roller conveyance mechanisms 111 and 113 will be described.

  FIG. 1 is a perspective view showing a roller transport unit according to the first embodiment of the present invention, FIG. 3 is a cross-sectional view showing a main part of the first roller transport mechanism according to the first embodiment of the present invention, and FIG. FIG. 5 is an exploded perspective view showing the main part of the first roller transport mechanism in the first embodiment of the present invention, and FIG. 5 shows the main part of the second roller transport mechanism in the first embodiment of the present invention. FIG. 6 is an exploded perspective view showing a main part of the second roller transport mechanism in the first embodiment of the present invention.

  In the figure, 121 is a roller transport unit, 122 is an inner guide that forms the medium transport path Rt2 (FIG. 2), 111 and 113 are first and second roller transport mechanisms, 22, and 24 are registration rollers, and 23 and 25, respectively. The pressure roller 42 is formed of a sheet metal that is a conductive material, directly holds the registration rollers 22, 24, and serves as a first holding portion that indirectly holds the pressure rollers 23, 25 and is driven It is a frame member as a roller holding part.

  Reference numeral 140 denotes a bearing as a first support member that rotatably supports the registration rollers 22 and 24 with respect to the frame member 42, and reference numerals 141 and 241 denote second holding portions that hold the pressure rollers 23 and 25. This is a bearing holder as a driven roller holding portion. The bearing holder 141 moves relative to the frame member 42 in the direction of arrow A along the line connecting the axes of the registration roller 22 and the pressure roller 23 (in this embodiment, the pressure roller 23 is moved closer to the registration roller 22. The bearing holder 241 connects the shafts of the registration roller 24 and the pressure roller 25 with respect to the frame member 42. The bearing holder 241 is slidably disposed in a direction away from the registration roller 22. Along the line, in the direction of arrow B (in this embodiment, the direction in which the pressure roller 25 is moved closer to or away from the registration roller 24) and is slidable. .

  Reference numeral 143 urges the bearing holders 141 and 241 with a predetermined urging force toward the direction in which the pressure rollers 23 and 25 approach the registration rollers 22 and 24, respectively, and the pressure roller 23 is applied to the registration roller 22 and the pressure roller. A spring 240 serving as the urging member that presses 25 against the registration roller 24, and a bearing 240 serving as a second support member that rotatably supports the pressure rollers 23 and 25 with respect to the bearing holders 141 and 241 respectively.

  In order to bias the bearing holders 141 and 241 toward the direction in which the pressure rollers 23 and 25 approach the registration rollers 22 and 24 by the spring 143, respectively, on the line connecting the axes of the registration roller 22 and the pressure roller 23, The registration roller 22 is positioned between the spring 143 and the pressure roller 23, and the registration roller 24 is positioned between the spring 143 and the pressure roller 25 on a line connecting the axes of the registration roller 24 and the pressure roller 25. Be made.

  The pressure roller 23, the bearing holder 141, the spring 143, and the bearing 240 constitute a pressure roller unit 150 as a first pressing unit. The pressure roller unit 150 is disposed between the registration roller 22 and the pressure roller 23. Is moved in the direction of arrow A with respect to the frame member 42 in accordance with the thickness of the sheet passing through the frame. The pressure roller 25, the bearing holder 241, the spring 143, and the bearing 240 constitute a pressure roller unit 250 as a second pressing unit. The pressure roller unit 250 is disposed between the registration roller 24 and the pressure roller 25. Is moved in the direction of arrow B with respect to the frame member 42 in accordance with the thickness of the sheet passing through the frame.

  The frame member 42, the bearings 140 and 240, the bearing holders 141 and 241, the spring 143, and the like are disposed at both ends of the registration rollers 22 and 24 and the pressure rollers 23 and 25. A gear (not shown) is attached to one end of each of the registration rollers 22 and 24, and a rotation transmission system (not shown) is disposed between the gear and the transport motor.

  The registration rollers 22 and 24 include roller main body portions 22a and 24a and shaft end portions 22b and 24b formed to protrude from both ends of the roller main body portions 22a and 24a, respectively. The bearing 140 is rotatably supported. The pressure rollers 23 and 25 include roller body portions 23a and 25a and shaft end portions 23b and 25b formed to protrude from both ends of the roller body portions 23a and 25a, respectively. At 25b, it is rotatably supported by a bearing 240.

  Each of the bearings 140 and 240 is a sliding bearing, and includes a cylindrical portion 40a and a flange portion 40b formed at one end of the cylindrical portion 40a so as to protrude radially outward. The inner peripheral surface of the support hole 40c formed through the portion 40a and the outer peripheral surfaces of the shaft end portions 22b to 25b are frictionally slid.

  The bearing holders 141 and 241 are held by the frame member 42 on one end side so that the bearing holders 141 and 241 do not rotate with respect to the frame member 42 with the rotation of the registration roller 22 and the pressure roller 23. For this purpose, a bearing holder holding part 225 is formed at a predetermined position of the frame member 42 so as to protrude from the edge part eg1. The bearing holder holding portion 225 is notched to a predetermined depth, and houses one end of the bearing holders 141 and 241 and also has a recess 42a as a first holder locking portion for locking, A tab 42b is provided as a pair of holder gripping portions formed by raising the side edges and as a rotation restricting portion. The tab 42b slidably holds the bearing holders 141 and 241 from both sides, and restricts the rotation of the bearing holders 141 and 241.

  A through hole 42c as a pressed member support portion for supporting the registration roller 22 is formed adjacent to the inner side (the other end side of the bearing holders 141 and 241) of the recess 42a in the frame member 42, The bearing 140 is inserted into the through hole 42c. The bearing 140 is held by the frame member 42 so as not to rotate with respect to the frame member 42 as the registration roller 22 rotates. Therefore, the through hole 42c has a track shape formed by connecting two arc-shaped portions a1 by a straight portion a2. Further, the outer peripheral surfaces of the cylindrical portion 40a and the flange portion 40b of the bearing 140 have a track shape like the through hole 42c.

  A spring retainer 42e is formed as a first urging member holding portion that is adjacent to the inside of the through hole 42c and is raised by cutting and supporting one end of the spring 143. A locking hole 42f as a second holder locking portion for locking the other ends of the bearing holders 141 and 241 is formed adjacent to the inside of the presser 42e. Both the spring retainer 42e and the locking hole 42f have a rectangular shape.

  The bearing holders 141 and 241 are formed of a rectangular cylindrical body having a horizontally long (or vertically long) shape (a shape in which a line connecting the axes of the registration roller 22 and the pressure roller 23 extends in the longitudinal direction). A pressure roller support portion 231 for supporting the spring 23, and a spring accommodating portion 232 for accommodating the spring 143. In order to prevent the bearing holders 141 and 241 from being detached from the frame member 42, a pair of locking pieces 41a are formed at one end of the bearing holders 141 and 241 so as to correspond to the tabs 42b and protrude leftward and rightward. The locking piece 41b is formed at the other end so as to protrude downward in correspondence with the locking hole 42f, and the locking piece 41b is in contact with the frame member 42 in the state where the locking piece 41b is in contact with the frame member 42. 41a and the inner peripheral edge of the recess 42a are locked, and the locking piece 41b and the inner peripheral edge of the locking hole 42f are locked.

  The pressure roller unit 150 is moved in the direction of the arrow A with respect to the frame member 42 according to the thickness of the sheet passing between the registration roller 22 and the pressure roller 23, and the pressure roller unit 250 is The locking pieces 41a and 41b and the frame member 42 are engaged with each other while the frame member 42 is moved in the arrow B direction according to the thickness of the paper passing between the registration roller 24 and the pressure roller 25. The positions, dimensions, and the like of the recesses 42a, the locking holes 42f, and the locking pieces 41a and 41b are set so that the stopped state can be maintained.

  The pressure roller support portion 231 is formed with a through hole 41c as a pressing member support, and the bearing 240 is fitted into the through hole 41c. The bearing 240 is held by the bearing holders 141 and 241 so that the bearing 240 does not rotate with respect to the bearing holders 141 and 241 as the pressure roller 23 rotates. For this purpose, the through hole 41c has a track shape formed by connecting two arc-shaped portions b1 by a straight portion b2. Further, the outer peripheral surfaces of the cylindrical portion 40a and the flange portion 40b of the bearing 240 have a track shape like the through hole 41c.

  The spring accommodating portion 232 is formed with a through hole 41 e so that the spring retainer 42 e can enter the bearing holders 141 and 241 when the bearing holders 141 and 241 are attached to the frame member 42. For this purpose, two arms am1 and am2 are formed on the pressure roller support portion 231 so as to protrude in parallel with each other, and the tips of the arms am1 and am2 are connected to support the other end of the spring 143. A spring receiving portion 41f as an urging member holding portion is formed. Between the spring retainer 42e and the spring receiving portion 41f, one end is brought into contact with the spring retainer 42e and the other end is brought into contact with the spring receiving portion 41f. The spring 143 is disposed in a compressed state. In the present embodiment, a compression spring is used as the spring 143.

  In the state in which the bearing holders 141 and 241 are attached to the frame member 42, the spring retainer 42e is provided between the through hole 41c and the spring receiver 41f, and the through hole 42c is provided between the through hole 41c and the spring retainer 42e. Be positioned. Further, on the surface of the spring receiving portion 41f and the spring retainer 42e facing the spring receiving portion 41f, a projection 233 having a predetermined shape, in this embodiment, is formed so that the spring 143 does not come off. The

  In this way, the spring retainer 42e is used as a reference, and the bearing holders 141, 241 are urged from the pressure rollers 23, 25 toward the registration rollers 22, 24 by the urging force of the spring 143. 25 can be sufficiently pressed against the registration rollers 22 and 24. Therefore, it is not necessary to dispose a spring inside the pressure rollers 23 and 25 on the line connecting the axes of the registration rollers 22 and 24 and the pressure rollers 23 and 25. As a result, the first and second roller transport mechanisms 111 and 113 can be reduced in size.

  Next, the operation of the roller transport unit 121 will be described. In this case, since the first and second roller transport mechanisms 111 and 113 have the same structure, the operation of the first roller transport mechanism 111 will be described.

  FIG. 7 is a first diagram for explaining the operation of the first roller transport mechanism in the first embodiment of the present invention, and FIG. 8 is the first roller transport mechanism in the first embodiment of the present invention. It is a 2nd figure for demonstrating operation | movement of.

  First, when a print command is received from a host computer (not shown) as a host device, the printer Pr (FIG. 2) starts printing.

  Along with this, the paper P stored in the paper cassette 34 is fed out by the pickup roller 103, separated one by one by the discriminator, transported through the medium transport path Rt 1, and supplied to the first roller transport mechanism 111. The At this time, in the first roller transport mechanism 111, the registration roller 22 and the pressure roller 23 are stopped.

  At this time, in the first roller conveyance mechanism 111, the spring 143 is disposed in a compressed state between the spring retainer 42e and the spring receiving portion 41f, so that as shown in FIG. 7, the spring receiving portion 41f receives the reaction force F1 represented by the urging force of the spring 143 and tries to move away from the spring retainer 42e. Accordingly, the bearing holder 141 conveys the paper P corresponding to the urging force of the spring 143. A pressing force F2 required for the above is generated, and the pressure roller 23 is pressed against the registration roller 22 with the pressing force F2, and a nip portion 52 is formed between the registration roller 22 and the pressure roller 23. The pressing force F2 is a resultant force of the reaction force F1 of each spring 143 disposed at both ends of the registration roller 22 and the pressure roller 23.

  When the sheet P hits the nip portion 52 with the registration roller 22 and the pressure roller 23 being stopped, the skew of the sheet P is corrected.

  Subsequently, when the conveyance motor is driven, the registration roller 22 and the pressure roller 23 are rotated in the direction of the arrow as shown in FIG. When the paper P enters the nip portion 52, the pressure roller 23 is moved away from the registration roller 22 against the pressing force F2.

  As a result, the paper P sandwiched between the registration roller 22 and the pressure roller 23 in the nip portion 52 receives the frictional force generated by the pressing force F <b> 2 and is conveyed in the arrow C direction as the registration roller 22 rotates.

  Thus, in the present embodiment, the frame member 42 is formed with the through hole 42c for supporting the registration rollers 22 and 24 and the spring presser 42e for holding the spring 143, and the bearing holders 141 and 242 are formed. A through hole 41c for supporting the pressure rollers 23 and 25 and a spring receiving part 41f for holding the spring 143 are formed, and a spring retainer 42e is disposed between the through hole 42c and the spring receiving part 41f. Since the spring 143 is disposed between the spring retainer 42e and the spring receiving portion 41f, the structure of the first and second roller transport mechanisms 111 and 113 can be simplified. Further, the urging force of the spring 143 can be reliably transmitted to the pressure rollers 23 and 25 via the bearing holders 141 and 242, and the pressing force F <b> 2 necessary for transporting the paper P can be sufficiently generated. .

  Furthermore, a spring 143 can be disposed on the inner side of the registration rollers 22 and 24 on the line connecting the axes of the registration rollers 22 and 24 and the pressure rollers 23 and 25, and the first and second roller transport mechanisms 111, The structure outside the pressure rollers 23 and 25 in 113 can be simplified. As a result, the first and second roller transport mechanisms 111 and 113 can be downsized, and the printer Pr can be downsized.

  In addition, since the spring 143 is disposed in a compressed state between the spring retainer 42e and the spring receiving portion 41f, when the same urging force is generated, the occupied space is smaller than when it is disposed in the extended state. can do. Therefore, the first and second roller transport mechanisms 111 and 113 can be reduced in size.

  Further, the rotation from the conveying motor is transmitted to the registration rollers 22 and 24 arranged at predetermined positions on the frame member 42, and the rotation transmitted to the registration rollers 22 and 24 moves relative to the frame member 42. Since it is transmitted to the pressure rollers 23 and 25 that are freely arranged, the registration rollers 22 and 24 and the pressure rollers 23 and 25 can be rotated reliably and stably.

  Since the through hole 42c is positioned between the through hole 41c and the spring retainer 42e, the bearing 140 fitted into the through hole 42c is interposed between the bearing 240 fitted into the through hole 41c and the spring retainer 42e. It can be arranged. Therefore, in the axial direction, the registration rollers 22 and 24 can be disposed close to the frame member 42, and the first and second roller transport mechanisms 111 and 113 can be further downsized.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 9 is a perspective view showing a roller transport unit according to the second embodiment of the present invention, and FIG. 10 is a diagram showing a main part of the second roller transport mechanism according to the second embodiment of the present invention.

  In the figure, 121 is a roller transport unit, 122 is an inner guide that forms a medium transport path Rt2 (FIG. 2), 111 and 113 are first and second roller transport mechanisms as first and second medium transport devices. , 22 and 24 are first rollers, driving rollers and registration rollers as pressed members, and 23 and 25 are second rollers, driven rollers and pressure members as pressure members. The rollers 42 are formed of a sheet metal made of a conductive material, and directly hold the registration rollers 22 and 24 and indirectly hold the pressure rollers 23 and 25 and hold a driving roller. It is a frame member as a part.

  Reference numeral 340 denotes a first support member that is made of a predetermined material, in the present embodiment, a metal material that is a conductive material, and supports the registration rollers 22 and 24 rotatably with respect to the frame member 42. The bearings 341 and 441 are bearing holders as a second holding part for holding the pressure rollers 23 and 25 and as a driven roller holding part. The bearing holder 341 is disposed so as to be movable and slidable in the direction of arrow A along the line connecting the axes of the registration roller 22 and the pressure roller 23 with respect to the frame member 42. The frame member 42 is slidably disposed in the direction of arrow B along a line connecting the axes of the registration roller 24 and the pressure roller 25 with respect to the frame member 42.

  Reference numeral 143 urges the bearing holders 341 and 441 with a predetermined urging force toward the direction in which the pressure rollers 23 and 25 approach the registration rollers 22 and 24, respectively. A spring 440 as an urging member that presses 25 against the registration roller 24 is formed of a metal material that is a conductive material, and the pressure rollers 23 and 25 are rotatably supported by the bearing holders 341 and 441, respectively. 2 is a bearing as a support member of 2;

  The pressure roller 23, the bearing holder 341, the spring 143, and the bearing 440 constitute a pressure roller unit 350 as a first pressing unit, and the pressure roller unit 350 is disposed between the registration roller 22 and the pressure roller 23. The frame member 42 is moved in the direction of arrow A in accordance with the thickness of the sheet as the medium passing through the frame. The pressure roller 25, the bearing holder 441, the spring 143, and the bearing 440 constitute a pressure roller unit 450 as a second pressing unit, and the pressure roller unit 450 is disposed between the registration roller 24 and the pressure roller 25. Is moved in the direction of arrow B with respect to the frame member 42 in accordance with the thickness of the sheet passing through the frame.

  A spring mounting portion 301 as a conductive member support portion and a biasing member support portion protrudes from a predetermined portion of the bearing holders 341 and 441, in this embodiment, to the arm am2 of the bearing holders 341 and 441. The torsion spring 302 as a conducting member formed of a metal material which is a conductive material is attached to the spring attachment portion 301. The torsion spring 302 includes a winding portion 311 wound by a predetermined number of turns, and first and second arm portions 312 and 313 formed to extend from both ends of the winding portion 311. The cylindrical boss portion 321 formed on the attachment portion 301 is attached to the spring attachment portion 301 by fitting into the winding portion 311.

  One end of the torsion spring 302, that is, the working end 316 of the first arm portion 312 is made to enter the bearing holder 441 through a hole 443 formed in the side surface of the bearing holder 441, and a cylinder (not shown) of the bearing 440 is formed. It is pressed against the shaped part with a predetermined urging force. The other end of the torsion spring 302, that is, the fixed end 317 of the second arm portion 313, together with the lead wire 45 a connected to one terminal of the resistance element 45, is fixed to the frame member 42 by a screw 47 as a fixing member. Fixed to. The fixed end 317 and the lead wire 45a of the second arm portion 313 and the frame member 42 are insulated by an insulating material or the like.

  Then, the lead wire 45b connected to the other terminal of the resistance element 45 extends downward through the hole h1 formed in the frame member 42, and is a predetermined metal part in the printer Pr (FIG. 2), for example, a housing. Fixed to the body and grounded.

The resistance value of the bearing 440 is about 1 × 10 ² [Ω], the resistance value of the resistance element 45 is about 1 × 10 ⁸ [Ω], and the working end 316 of the first arm portion 312 is a cylinder of the bearing 440. The urging force pressed against the shape portion is about 200 [gf].

  The center cn1 of the boss portion 321 is disposed at a predetermined distance from an imaginary straight line connecting the axis sh1 of the pressure roller 25 and the center cn2 of the screw 47.

  Next, the operation of the first and second roller transport mechanisms 111 and 113 will be described. Since the first and second roller transport mechanisms 111 and 113 have the same structure, the operation of the second roller transport mechanism 113 when the paper passes between the registration roller 24 and the pressure roller 25 will be described.

  FIG. 11 is a diagram for explaining the operation of the second roller transport mechanism according to the second embodiment of the present invention.

  In the figure, 14 is a photosensitive drum as an image carrier, 20 is a transfer roller as a transfer member, 24 is a registration roller, 25 is a pressure roller, 143 is a spring, and 441 is a bearing holder.

  The sheet P fed from the sheet cassette 34 (FIG. 2) as the first medium stacking section and the medium storage section by the first medium feeding section 21 and supplied to the medium transport path Rt1 is the first medium loading section Rt1. The roller transport mechanism 111 temporarily stops and the skew feeding is corrected, and then supplied to the second roller transport mechanism 113.

  When the front end of the sheet P reaches between the registration roller 24 and the pressure roller 25, the pressure roller 25 is moved in a direction away from the registration roller 24 (upward in FIG. 11) against the urging force of the spring 143. . At this time, the spring receiving portion 41f (FIG. 3) receives a reaction force F1 represented by the urging force of the spring 143, and the bearing holder 441 is necessary for transporting the paper P corresponding to the urging force of the spring 143. A pressing force F2 is generated, and the pressure roller 25 is pressed against the registration roller 24 with the pressing force F2.

  Subsequently, when the front end of the sheet P reaches the transfer portion p1 between the photosensitive drum 14 and the transfer roller 20, a high voltage is applied to the transfer roller 20 by the high-voltage power supply 61. A toner image as a developer image is transferred onto the paper P. At this time, a high voltage is also applied to the registration roller 24 and the pressure roller 25 via the paper P. However, the pressure roller 25 is supported by the bearing 440, and the bearing 440, the torsion spring 302, the lead wire 45a, and the resistance element 45. And grounded via the lead wire 45b, a current corresponding to the resistance value of the bearing 440 and the resistance element 45 flows to the ground.

  Therefore, a high voltage is not applied to a portion made of a metal material existing in the vicinity of the registration roller 24 and the pressure roller 25, and no current flows or discharges. The toner forming the toner image is not scattered by static electricity, and the toner image can be transferred onto the paper P satisfactorily. As a result, the image quality does not deteriorate. Further, since a high voltage is not applied to the electronic components existing in the vicinity of the pressure roller 25, the printer Pr is not damaged.

  Subsequently, when the trailing edge of the sheet P passes between the registration roller 24 and the pressure roller 25, the pressure roller 25 is pressed against the registration roller 24 by the urging force of the spring 143.

  By the way, when the pressure roller 25 is pressed against the registration roller 24, the bearing holder 441 is moved in the same direction by the thickness of the paper P together with the pressure roller 25. At this time, since the torsion spring 302 is attached to the spring attachment portion 301, the positional relationship between the working end 316 (FIG. 10) of the first arm portion 312 and the bearing 440 of the pressure roller 25 does not change. Therefore, regardless of the thickness of the paper P, the torsion spring 302 contacts the bearing 440 with a constant biasing force.

  Thus, in the present embodiment, the pressure roller 25, the bearing 440, and the torsion spring 302 are all formed of a conductive metal material, and one end of the torsion spring 302 is brought into contact with the bearing 440. Since the other end is fixed by the screw 47, regardless of the thickness of the paper P, the pressure roller 23 can be pressed against the registration roller 22 with a stable pressing force F2, and the pressure roller 25 can be grounded.

  The torsion spring 302 is attached to the spring attachment portion 301 by fitting the boss portion 321 of the spring attachment portion 301 into the winding portion 311, and the center cn <b> 1 of the boss portion 321 is the axis sh <b> 1 of the pressure roller 25. Since the bearing holder 441 moves together with the pressure roller 25, the torsion spring 302 is sufficiently bent. Therefore, excessive stress is not applied to the screw 47.

  Since the torsion spring 302 is brought into contact with the bearing 440 and does not directly contact the pressure roller 25, the wear resistance of the pressure roller 25 and the torsion spring 302 can be improved.

  In the first and second embodiments, the first and second roller transport mechanisms 111 and 113 are described. However, the present invention is applied to another roller transport mechanism including a roller pair. Can do.

  In each of the above embodiments, the printer Pr has been described. However, the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

22, 24 Registration roller 23, 25 Pressure roller 41c, 42c Through hole 41f Spring receiving portion 42 Frame member 42e Spring presser 111, 113 First and second roller transport mechanisms 141, 241, 341, 441 Bearing holder 143 Spring

Claims (10)

(A) a pressed member;
(B) a first holding unit for holding the pressed member;
(C) a pressing member disposed to face the pressed member;
(D) a second holding portion that is movably disposed with respect to the first holding portion and holds the pressing member;
(E) a biasing member that presses the pressing member against the pressed member;
(F) The first holding portion includes a first urging member holding portion that holds one end of the urging member,
(G) The second holding portion includes a second biasing member holding portion that holds the other end of the biasing member,
(H) In the direction in which the pressing member is pressed against the pressed member, the second urging member holding portion is disposed on the downstream side of the first urging member holding portion,
(I) The urging member is a compression spring, and is disposed between the first urging member holding part and the second urging member holding part. (A) The pressing member is a driven roller having a first rotating shaft,
(B) The pressed member is a drive roller having a second rotating shaft,
(C) The medium conveying device according to claim 1, wherein the urging member is disposed on an imaginary line passing through the first and second rotating shafts. In the direction in which the pressing member is pressed against the pressed member, the first rotating shaft, the second rotating shaft, the first biasing member holding portion, and the second biasing member holding portion are arranged in this order from the upstream side to the downstream side. The medium conveying apparatus according to claim 2 , wherein the medium conveying apparatus is disposed.   The pressed member support portion that supports the pressed member is positioned between the pressing member support portion that supports the pressing member and the first biasing member holding portion. The medium carrying device according to item.   The medium conveying apparatus according to claim 1, wherein the urging member is disposed in a compressed state. (A) In the pressed member support portion, the pressed member is supported by the first support member with respect to the first holding portion,
(B) In the press member support portion, the press member is supported by the second support member with respect to the second holding portion. (A) The pressing member and the second support member are formed of a conductive material,
(B) One end of a conducting member formed of a conductive material is brought into contact with the second support member, and the other end is fixed by a fixing member,
(C) The medium conveying apparatus according to claim 6, wherein the pressing member is grounded via the second support member, a conduction member, and a fixing member.   The medium conveying apparatus according to claim 7, wherein the conducting member is attached to a conducting member support portion formed in the second holding portion. (A) The conducting member is a torsion spring, and is attached to the conducting member support portion by fitting a boss portion of the conducting member support portion into a winding portion of the torsion spring.
(B) The medium conveyance according to claim 8, wherein the center of the boss part is disposed at a predetermined distance from an imaginary straight line connecting the axis of the pressing member and the center of the fixing member. apparatus.   An image forming apparatus on which the medium conveyance device according to claim 1 is mounted.

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